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Chromosome 15 Ring

National Organization for Rare Disorders, Inc.

ImportantIt is possible that the main title of the report Chromosome 15 Ring is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.

Synonyms

Ring 15

Ring 15, Chromosome

r15

Ring 15, Chromosome (mosaic pattern)

Disorder Subdivisions

None

General Discussion

Chromosome 15 Ring results from loss (deletion) of genetic material from both ends of the 15th chromosome and a joining of the ends to form a ring. Chromosomes are found in the nucleus of all body cells. They carry the genetic characteristics of each individual. Pairs of human chromosomes are numbered from 1 through 22, with an unequal 23rd pair of X and Y chromosomes for males and two X chromosomes for females. Each chromosome has a short arm designated as "p" and a long arm identified by the letter "q". Chromosomes are further subdivided into bands that are numbered.

In individuals with Chromosome 15 Ring, the variability of associated symptoms and findings may depend upon the amount and location of genetic material lost from the 15th chromosome, the stability of the ring chromosome during subsequent cellular divisions, or other factors. Evidence suggests that the clinical features seen in Chromosome 15 Ring appear to result from deletions of genetic material from the long arm (q) of chromosome 15 (known as "monosomy 15q"), with the ring chromosome typically replacing a normal 15th chromosome. In addition, in some cases, only a certain percentage of an individual's cells may contain Chromosome 15 Ring, while other cells may have a normal chromosomal makeup (a finding known as "chromosomal mosaicism"), potentially affecting the variability of associated symptoms and findings.

In most cases, Chromosome 15 Ring appears to be caused by spontaneous (de novo) errors very early in embryonic development. In such cases, the parents of the affected child usually have normal chromosomes and a relatively low risk of having another child with the chromosomal abnormality. However, there have been rare cases in which a parent of an affected individual also has Chromosome 15 Ring. In such instances, the chances are greater of having another child with the chromosomal abnormality. In addition, a few cases have been reported in which Chromosome 15 Ring has been the result of a "balanced translocation" in one of the parents. Translocations occur when regions of certain chromosomes break off and are rearranged, resulting in shifting of genetic material and an altered set of chromosomes. If a chromosomal rearrangement is balanced, meaning that it consists of an altered but balanced set of chromosomes, it is usually harmless to the carrier. However, such a chromosomal rearrangement may be associated with an increased risk of abnormal chromosomal development in the carrier's offspring.

Chromosomal analysis and genetic counseling are typically recommended for parents of an affected child to help confirm or exclude the presence of Chromosome 15 Ring, potential mosaicism, or a balanced translocation in one of the parents.

Many individuals with Chromosome 15 Ring have some features similar to those associated with Russell-Silver syndrome (RSS), which is a genetic disorder characterized by growth deficiency and short stature, distinctive facial abnormalities, and other features. (For further information, please see the "Related Disorders" section below.) In some of these cases, genetic analysis has indicated that the prenatal and postnatal growth retardation associated with Chromosome 15 Ring (and potentially suggestive of RSS) may result from deletion of a gene known as the insulin-like growth factor I receptor (IGF1R) gene, which has been mapped to the long arm of chromosome 15 (15q25-q26).

For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders (NORD). A copy of the complete report can be downloaded free from the NORD website for registered users. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational therapies (if available), and references from medical literature. For a full-text version of this topic, go to www.rarediseases.org and click on Rare Disease Database under "Rare Disease Information".

The information provided in this report is not intended for diagnostic purposes. It is provided for informational purposes only. NORD recommends that affected individuals seek the advice or counsel of their own personal physicians.

It is possible that the title of this topic is not the name you selected. Please check the Synonyms listing to find the alternate name(s) and Disorder Subdivision(s) covered by this report

This disease entry is based upon medical information available through the date at the end of the topic. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder.

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